RTD-Probe-Only

Supported Applications

The ACI Platinum RTD Probe Only series consists of temperature sensors designed for use with electronic controllers in commercial heating and cooling building management systems. The probe-only configuration is intended for installation within thermowells or direct insertion into ducts, pipes, and vessels where a separate connection head is not required. Documented applications include roof top units, air handlers, supply/discharge/return/mixed/exhaust air duct temperature sensing, immersion temperature sensors in hydronic water systems, and replacement of existing temperature sensors.

Operating Conditions & Performance

The series utilizes Platinum RTD elements conforming to DIN EN 60751 (IEC 751) with a temperature coefficient of 3850 ppm/°C. The sensor operating temperature range is -40 to 200°C (-40 to 392°F), while the storage temperature range is -40 to 85°C (-40 to 185°F). Ambient humidity ratings are specified as 10 to 95% RH, non-condensing.

Accuracy for Class A sensors follows the tolerance formula: ±/− °C = (0.15 °C + (0.002 * |t|)), where |t| is the absolute value of temperature above or below 0°C in °C. Specific accuracy points include:

• At -40°C (-40°F): ±/− 0.23°C (+/- 0.414°F)
• At 0°C (32°F): ±/− 0.15°C (+/- 0.27°F)
• At 200°C (392°F): ±/− 0.55°C (+/- 0.99°F)

Sensor stability is rated at +/- 0.03% after 1000 hours @ 300°C (572°F). The nominal response time for a 63% step change is 8 seconds.

Configuration Options

The series offers configurable probe lengths, wire configurations, and lead insulation types to accommodate specific installation requirements. Sensors are manufactured using ACI's double encapsulation process with high-quality thermally conductive epoxy to eliminate moisture effects and increase thermal response time.

Probe Dimensions & Materials

The probe features a 0.250" (6.35mm) diameter sheath constructed of 304 Stainless Steel. Available insertion lengths include:

• 2.00" ± 0.13"
• 4.00" ± 0.13"
• 6.00" ± 0.13"
• 8.00" ± 0.13"
• 12.00" ± 0.25"
• 18.00" ± 0.25"

Note: No flare is present on probes of 6 inches and under.

Sensor Elements & Wiring

The series supports two nominal resistance values at 0°C (32°F): A/100-xW-PO Series with 100 Ohms nominal, and A/1K-xW-PO Series with 1000 Ohms nominal. Configurations are available in:

• Two-wire: Non-polarity sensitive
• Three-wire: Polarity sensitive (recommended for use with 3-Wire temperature transmitters or PLC configurations to compensate for external lead wire resistance)

Lead wires are available in two insulation types:

• Standard Wire: Etched Teflon (PTFE) colored leads, MIL-W-16878/4 Type E. Rated for -55°C (-67°F) to 200°C (392°F). Suitable for indoor and outdoor wet locations; resistant to oil, moisture, acids.
• Plenum Wire: CL2P FEP (Fluorinated Ethylene Propylene), Type CMP. Rated for -80°C (-112°F) to 150°C (302°F). Suitable for indoor and outdoor wet locations; resistant to oil, gas, sunlight, abrasion, and acid.

Standard lead lengths are 14" (35.6 cm) for probes up to 8 inches and 24" (61 cm) for 12-inch and 18-inch probes. Plenum cable options include 6 ft, 10 ft, or 20 ft lengths.

Approvals & Accessories

The series carries CE, RoHS2, and WEEE approvals. NIST Certificates (3 Points) are available as an option. Thermal grease accessories include NSG HEAT TRANSFER PASTE in 2 oz tubes or 16 oz jars.

Key Product Differences

Variants within the series differ primarily by sensor resistance, wire count, probe insertion length, and lead insulation type. The A/100-xW-PO models provide a 100 Ohm nominal output at 0°C (32°F), while A/1K-xW-PO models provide a 1000 Ohms nominal output. Self-heating characteristics vary by resistance: the 100 Ohm RTD is rated at 7 mW/°C in still air with a maximum operating current of 5 mA, whereas the 1K Ohm RTD is rated at 4 mW/°C in still air with a maximum operating current of 3 mA.

Model numbers follow the format A/<model series>-<wire count>-PO-<probe length>-<lead wire options>-NIST. For example, A/1K-3W-PO-12" denotes a 1000 Ohm Platinum RTD with three wires in a probe-only configuration with a 12-inch insertion length.